Conduction device



April 3, 1956 H. D. DOOLITTLE CONDUCTION DEVICE Filed NOV. 28, 1952 INVENTOR HOW RD D. D LITTLE ATTORNE United States Patent CONDUCTION DEVICE Howard D. Doolittle, Stamford, Conn., assignor to Machlett Laboratories, Incorporated, Springdale, Conn., a corporation of Connecticut Application November 28, 1952, Serial No. 323,041

15 Claims. (Cl. 313-34) This invention concerns an improvement in conduction devices which employ a gas-tight envelope with at least a pair of electrodes therein. More particularly, this invention concerns a novel mercury electrode of the mercury soaked metallic sponge type for use in conduction devices.

The mercury soaked metallic sponge electrode has been demonstrated to have advantages over the more familiar mercury pool electrode. The sponge type electrode, like the liquid pool, aids in maintaining constant the interelectrode spacing between it and an adjacent electrode inasmuch as it resists damage which might occur to a more conventional electrode due to sputtering or burning. But unlike the liquid electrode, the sponge type electrode maintains its proper spacing to its adjacent electrode even when mounted in equipment which may be agitated, rocked or tipped from side to side, as might occur in its use aboard a ship, for example.

With mercury electrodes as heretofore constructed, it has been necessary to mount the electrode in the lowest portion of the gas-tight envelope so that condensed mercury vapors are able to return to the electrode under the influence of gravity. This limitation upon location has often prevented the positioning of mercury electrodes in various other places within a gas-tight envelope where they might function to better advantage. Furthermore, should more than one mercury electrode element be desirable within an envelope structure, it has been in convenient and usually impractical to construct a structure which has two low portions capable of accumulating distinct mercury pools. An even more diflicult problem occurs where it is desirable to have a pair of mercury electrodes so located that there can be proper interaction between them.

My invention makes possible the use of a mercury electrode in many new positions within a gas-tight envelope. It furthermore makes possible the use of a plurality of mercury electrodes located in a variety of posi.- tions relative to one another within one gas-tight envelope. In the practice of my invention a mercury soaked metallic sponge electrode may be located at any of various points within the gas-tight envelope other than the lowest point therein. This sponge electrode is supported upon the envelope walls, preferably upon the top or side walls. The support is accomplished in such a manner that the electrode is below and in communication with a surface upon which mercury vapor can condense. This arrangement permits condensed mercury to flow to the metallic sponge under the influence of gravity, thereby continually replacing evaporated mercury. The condensation surface may be advantageously incorporated as part of the electrode support structure. A collection member in which mercury which has been condensed may be collected and held in contact with the sponge ready for use may also be employed.

For a better understanding of my invention reference is made to the drawing which shows a typical conduction device,a spark gap, in which my novel electrode is used.

2,740,911 Patented Apr. 3, 1956 The structure shown in the drawing is substantially symmetrical about an axis of rotation corresponding to the major axis of the tube. The structure includes a pair of electrodes 10 and 11 enclosed within a gas-tight envelope. The surfaces of these electrodes are surfaces of revolution about the major axis of the structure. The gas-tight envelope consists of annular dielectric member 12 closed at one end by annular metallic member 13 and disc member 18 and closed at its other end by metallic cup 14.

The lip 14a of cup 14 is sealed to an inwardly turned portion 12a of annular insulator 12. The cup member 14 contains a porous iron sponge which, when mercury saturated, constitutes electrode 11. The electrode may be fluid cooled by passing cooling fluid through coils 16 which surround cup 14.

The other end 12b of dielectric member 12 is made re-entrant. This end 12b of dielectric member 12 is sealed to the outer peripheral edge portion 13b of annular metallic member 13 which has a somewhat distorted S- shaped cross section. The electrode 10 may be afiixed to annular metallic member 13 by aflixing the electrode 10 directly to member 13 at its inner peripheral edge portion 13a. In the alternative, the edge portion 13a of member 13 may be sealed to tubular metallic member 17, which member is in turn affixed to metallic disc 18, thereby completing the gas-tight envelope. In this event, the disc 18 is advantageously made to support the metallic sponge 19 which when mercury soaked constitutes electrode 10. Member 17 together with the disc 18 and end wall 23 which parallels disc 18 and which is sealed at its edges to tubular member 17 advantageously provide a cooling chamber 22. Cooling fluid is fed into the chamber 22 through an axial duct 24 and removed through another duct 25. Envelope portion 13a by virtue of its good conduction path to chamber 22 provides a cooling surface in communication with metallic sponge 19. Shoulder 20 atop metallic sponge 19 is in communication with cooling surface 13a, and it is so inclined to the axis of rotation that it provides an annular trough adjacent the metallic sponge 19 which trough collects liquid mercury 26 for eventual absorption by said sponge.

The porous metallic sponge members 15 and 19 are advantageously composed of a porous sintered compact of iron powder. The sponge may be made by compacting carbonyl iron particles of high purity under a pressure in the order of 3000 pounds per square inch, then heating the compacted iron in a furnace for one hour at a temperature of 1000 C. while passing hydrogen through the furnace in order to thoroughly clean the iron mass and completely sinter the particles together. In order to hold the sponge electrodes in place, it may be necessary to employ metallic members such as strips anchored to the supporting members, cup 14 and/or disc 18, in such a manner that they extend into the sintered metallic mass. In the case of the spark gap as shown here, it may be desirable to introduce an atmosphere of pure gases, such as hydrogen and argon, into the device prior to sealing off the exhaust tubulation (not shown). The use of such gases provides a readily ionizable medium for conduction. The pressure of gas introduced should be governed by the factors which will provide optimum conduction conditions and'hold off potential.

The use of mercury electrode devices, including those employing my invention, is limited to one position. The

spark gap must be mounted in equipment upright andalso takes place when vapor contacts the fluid cooled metallic surface of member 13adjacent edge 1311. Thereafter, gravity flow causes the mercury so condensed to accumulate in the trough formed on sponge member 19. The mercury 26 in the trough will replace that evaporated from electrode 10. In addition to its condensation function, cooling chamber 22 tends to cool electrode 10, just as cooling coil 16 tends to do in the case of electrode 11. This cooling function is important because the heat dissipated by the discharge within the gap would otherwise raise the temperature of the electrode to the point Where vaporization of the mercury becomes excessive and the rate of replacement is inadequate. In that event, the intense spark in the gap between electrodes and 11 might burn or otherwise damage one of the metallic sponges.

A spark gap of the type described is particularly valuable in applications where a heavy reverse current is encountered. It is important in spark gap applications that the gap be maintained at a constant dimension in order to avoid changing the operating characteristics of the device. For applications, where the reverse current is as high as the forward current, such as in spark gap bombarder applications, an electrode which is not a mercury electrode will sputter and burn away. My invention makes available a spark gap which will not readily sputter and burn away and hence will maintain constant the gap between electrodes.

It should be noted that metallic sponges 15 and 19 may be made of molybdenum, tungsten or other material which may be formed into a sponge and which will not dissolve in mercury. Any metallic sponge otherwise capable of use in this application is satisfactory if it is capable of retaining a considerable quantity of mercury.

Other applications of my novel electrode, other than use in spark gaps, are possible. In such instances the electrode may be employed, not in a gaseous atmosphere, but rather in a vacuum or low pressure gaseous device. The support electrode need not be supported from the top of the gas-tight envelope but may be supported upon the side walls or other portions of the gas-tight envelope. A supporting member distinctly separate from the envelope may be employed and may or may not include as part of its structure some cooling means. Various types of cooling means may be employed in conjunction with surfaces internal of the gas-tight envelope upon which the mercury may be condensed. Various types of cooling are contemplated by my invention, provided that the cooling surfaces are in communication with the electrode so that the condensed mercury may flow to the electrode under the force of gravity.

I claim:

1. A conduction device for operation in only one position having a pair of mercury saturated metallic sponge electrodes within a gas-tight envelope, one of said elec trodes being supported upon anenvelope wall other than the bottom of the envelope and below and in communication with surfaces upon which mercury vapor can condense and flow under the influence of gravity to the metallic sponge.

2. A conduction device for operation in only one position having a pair of vertically spaced mercury saturated metallic sponge electrodes; within a gas-tight envelope, the upper of said electrodes being supported by the envelope by means; extending inwardly including a cooling surface for condensing mercury vapors.

3. A conduction device for operation in only one position having a pair of mercury saturated metallic sponge electrodes within a gas-tight envelope, one of said electrodes being supported upon means extending inwardly from the envelope walls and which has a cooling-surface above the electrode, said electrode having a collection trough on its surface adjacent the, cooling surface, which trough is so located that condensed-mercury collected in the trough from the cooling surface is in contact with the electrode.

4. A conduction device for operation in only one position having a pair of vertically spaced mercury saturated metallic sponge electrodes within a gas-tight envelope, one of said electrodes being supported upon means extending inwardly from the envelope walls and embodying a member which is provided with a cooling surface and which is of smaller horizontal diameter than the electrode.

5. A conduction device for operation in only one position having a pair of mercury saturated sponge electrodes within a gas-tight envelope one of said electrodes being of such shape that a surface thereof describes a surface of revolution which surface is coaxially fixed to a cylindrical support of smaller diameter than the electrode, which support includes a cooling surface.

6. A conduction device comprising a pair of mercury saturated metallic sponge electrodes within a gastight envelope, one of said electrodes being positioned in the lowest portion of the envelope to receive condensed mercury by its natural flow under gravity and the other electrode being supported by a support extending inwardly from the tube envelope, a portion of whose surface serves as a condensation surface.

7. A conduction device comprising a pair of mercury saturated metallic sponge electrodes within a gas-tight envelope, one of said electrodes being positioned in the lowest portion of the envelope to receive condensed mercury by its natural flow under gravity and the other electrode being afiixed to the top of the envelope by a support member providing a condensation surface and having a collection trough positioned below the condensation surface such that condensed mercury collected in the trough is in contact with the sponge.

8. A spark gap employing two opposed mercury elcctrodes, each of said electrodes consisting of a mercury saturated metallic sponge located within a common gastight envelope, one of which electrodes is located in the lowest portion of the envelope in order to receive condensed mercury by its natural flow under gravity and the other of which electrodes is supported upon the vacuum envelope by a support which also provides a condensation surface.

9. A conduction device comprising a pair of mercury saturated metallic sponge electrodes within a gas-tight envelope, one of said electrodes comprising a mercury saturated sponge, which electrode is of such shape that its surface describes a surface of revolution including an annular collection trough for condensed mercury at its top surface and which electrode is coaxially supported at its top surface upon the vacuum envelope by a cylindrical support member which extends inwardly from the envelope and which includes a condensation surface.

10. A conduction device comprising a pair of mercury saturable metallic sponge electrodes within a gas-tight envelope, one of the electrodes being located in the envelope in position to receive condensed mercury by natural flow under gravitational force, a support mounted in the envelope and having a condensation surface thereon, and cooling means for the condensation surface, the second electrode being mounted on the support in position to receive condensed mercury by gravitational flow from the condensation surface.

11. A conduction device comprising a pair of mercury saturable metallic sponge electrodes within a gas-tight envelope, one of the electrodes being located in the envelope in position to receive condensed mercury by natural flow under gravitational force, a support member mounted in the envelope above said electrode and having a condensation surface thereon, the second electrode being mounted on the support in position to receive condensed merc ry by gravitational flow from the condensati'on surface.

12. A conduction device comprising a gas-tight envelope embodying an annular dielectric portion, a base member sealed to one end of the dielectric portion, an annular metallic member having its outer periphery sealed to the opposite end of the dielectric member, cooling means sealed within the central opening in the annular metallic member, a mercury saturable electrode supported inwardly of the envelope on said cooling means, and a second electrode within the envelope in predetermined spaced relation with the first electrode.

13. A conduction device comprising a gas-tight envelope embodying an annular dielectric portion, a base member sealed to one end of the dielectric portion, an annular metallic member having its outer periphery sealed to the opposite end of the dielectric member, cooling means sealed within the central opening in the annular metallic member, a mercury saturable metallic sponge electrode supported inwardly of the envelope on said cooling means, and a second mercury saturable metallic sponge electrode within the envelope below and in predetermined spaced relation with the first electrode.

14. A conduction device comprising a gas-tight envelope embodying an annular dielectric portion, a base member sealed to one end of the dielectric portion, an annular metallic member having its outer periphery sealed to the opposite end of the dielectric member, cooling means sealed within the central opening in the annular metallic member, a mercury saturable metallic sponge 6 electrode supported inwardly of the envelope on said cooling means, and a second mercury saturable metallic sponge electrode mounted on the base member in predetermined spaced relation with the first electrode.

15. A conduction device comprising a gas-tight envelope embodying an annular dielectric portion, a base member sealed to one end of the dielectric portion, an annular metallic member having its outer periphery sealed to the opposite end of the dielectric portion, a metal disc sealed throughout its periphery to the inner periphery of the annular metallic member, cooling means connected with the disc, a mercury saturable metallic sponge electrode supported by the disc and having a diameter substantially larger than the diameter of the disc, an annular portion of the surface of the electrode encircling the disc providing a surface for collecting condensed mercury, and a second mercury saturable metallic sponge electrode mounted on said base member in predetermined spaced relation with the first electrode.

References Cited in the file of this patent UNITED STATES PATENTS 1,274,691 Davis Aug. 6, 1918 2,468,037 Clark Apr. 26, 1949 2,617,064 Lewin Nov. 4, 1952 

1. A CONDUCTION DEVICE FOR OPERATION IN ONLY ONE POSITION HAVING A PAIR OF MERCURY SATURATED METALLIC SPONGE ELECTRODES WITHIN A GAS-TIGHT ENVELOPE, ONE OF SAID ELECTRODES BEING SUPPORTED UPON AN ENVELOPE WALL OTHER THAN THE BOTTOM OF THE ENVELOPE AND BELOW AND IN COMMUNICATION WITH SURFACES UPON WHICH MERCURY VAPOR CAN CONDENSE AND FLOW UNDER THE INFLUENCE OF GRAVITY TO THE METALLIC SPONGE. 